The present invention is directed to related apparatus systems, equipment and methods for heart surgery procedures.
Major heart surgery has been accomplished by procedures that require full cardiopulmonary bypass (CPB), and complete cessation of cardiopulmonary activity. Open heart surgery typically requires significant hospitalization and recuperation time for the patient. The average mortality rate with this type of procedure is low, but is associated with a complication rate that is often much higher compared to when cessation and CPB are not required. While very effective in many cases, the use of open heart surgery to perform various surgical procedures such as coronary artery bypass grafting (CABG) is highly traumatic to the patient. These procedures require immediate postoperative care in an intensive care unit, a period of hospitalization for at least several days, and an extended recovery period. In addition, open heart procedures require the use of CPB which continues to represent a major assault on a host of body systems. For example, there is noticeable degradation of mental faculties following such surgeries in a significant percentage of CABG patients. This degradation is commonly attributed to cerebral arterial blockage and emboli from debris in the blood generated by the use of CPB during the surgical procedure. At the same time, the dramatic increase in the life expectancy of the general population has resulted in patients that are more likely to be older and in poor health, with less cardiovascular, systemic, and neurologic reserve needed to recover from the trauma caused by the use of CPB. As a consequence, inflammatory, hemostatic, endocrinologic, and neurologic stresses are tolerated to a much lesser degree by a significant number of patients today, and play a more significant role in CPB-induced morbidity.
The CABG procedure generally involves open chest surgical techniques to treat diseased vessels. During this procedure, the sternum of the patient is cut in order to spread the chest apart and provide access to the heart. During surgery the heart is stopped, and by the use of CPB blood is diverted from the lungs to an artificial oxygenator. In general CABG procedures, a source of arterial blood is then connected to a coronary artery downstream from the occlusion. The source of blood is often an internal mamary artery, and the target coronary artery is typically among the anterior or posterior arteries which may be narrowed or occluded. The same or similar CPB procedure is used in conjunction with other cardiac surgical procedures, such as value repair or replacement and heart transplant.
The combined statistics of postoperative morbidity and mortality continue to illustrate the shortcomings of CPB. The extracorporeal shunting and artificially induced oxygenation of blood activates a system wide roster of plasma proteins and blood components in the body including those that were designed to act locally in response to infection or injury. When these potent actors are disseminated throughout the body without normal regulatory controls, the entire body becomes a virtual battleground. The adverse hemostatic consequences of CPB also include prolonged and potentially excessive bleeding. CPB-induced platelet activation, adhesion, and aggregation also contribute to a depletion in platelet number, and is further compounded by the reversibly depressed functioning of platelets remaining in circulation. The coagulation and fibrinolytic systems both contribute to hemostatic disturbances during and following CPB. However, the leading cause of morbidity and disability following cardiac surgery is cerebral complications. Gaseous and solid micro and macro emboli, and less often perioperative cerebral hypoperfusion, produce neurologic effects ranging from subtle neuropsychologic deficits to fatal stroke. Advances in computed tomography, magnetic resonance imaging, ultrasound, and other imaging and diagnostic techniques have added to the understanding of these complications. But with the possible exception of perioperative electroencephalography, these technologies do not yet permit real time surgical adjustments that are capable of preventing emboli or strokes in the making. Doppler and ultrasound evaluation of the carotid artery and ascending aorta, and other diagnostic measures, can help identify surgical patients at elevated risk for stroke and are among the growing list of pharmacologic and procedural measures for reducing that risk.
CPB also affects various endocrine systems, including the thyroid gland, adrenal medulla and cortex, pituitary gland, pancreas, and parathyroid gland. These systems are markedly affected not only by inflammatory processes, but also by physical and biochemical stresses imposed by extracorporeal perfusion. Most notably, CPB is now clearly understood to induce euthyroid-sick syndrome which is marked by profoundly depressed triiodothyronine levels persisting for days following cardiothoracic surgery. The efficacy of hormone replacement regimens to counteract this effect are currently undergoing clinical investigation. By contrast, levels of the stress hormones epinephrine, norepinephrine, and cortisol are markedly elevated during and following CPB, and hyperglycemia is also possible.
Alternatives to CPB are limited to a few commercially available devices that may further require major surgery for their placement and operation such as a sternotomy or multiple anastomoses to vessels or heart chambers. For example, some present day devices used in CPB may require a sternotomy and an anastomosis to the ascending aorta for placement. The main drawbacks of these devices include their limited circulatory capacity, which may not totally support patient requirements, and their limited application for only certain regions of the heart, such as a left ventricular assist device. Other available devices that permit percutaneous access to the heart similarly have disadvantages, such as their limited circulatory capabilities due to the strict size constraints for their positioning even within major blood vessels. Moreover, the relative miniaturization of these types of devices present a high likelihood of mechanical failure. In further attempts to reduce the physical dimensions for cardiac circulatory apparatus, the flow capacity of these devices is significantly diminished.
During cardiac surgery, the heart is either beating, in which case the heart continues to circulate the blood through the lungs to maintain the patient, or immobilized entirely in which case oxygenation and circulation of blood to maintain the patient requires use of CPB. Bypass surgery on a beating heart has been limited to only a small percentage of patients requiring the surgical bypass of an occluded anterior heart vessel. These patients typically could not be placed on CPB and were operated on while the heart was kept beating. These patients are at risk of having to be placed on CPB on an emergency basis in the event the heart stops or becomes unstable or is damaged during the surgical procedure on the beating heart. Meanwhile, patients requiring surgery on posterior or lateral heart vessels and whose hearts must be immobilized and placed on CPB often suffer major side effects as previously described.
The medical community is currently performing more beating heart bypass surgery in an effort to avoid the use of artificial heart-lung machines. The need is increasing for apparatus systems, methods and associated equipment to enhance the capability and versatility of beating heart surgery and to avoid CPB procedures in any heart surgery. The current trend toward thoracoscopic methods of performing bypass surgery, without opening the chest cavity, have resulted in limited success and applicability primarily due to the limited number of heart vessels which can be accessed through thorascopic methods. A major limitation of thorascopic bypass surgery methods is due to the fact that only the anterior heart vessels are accessible for surgery. More importantly, even open chest surgery providing full access to the heart also requires CPB when bypass surgery is performed on the lateral or posterior vessels of the heart, due to the fact that in conventional procedures the heart must be stopped when it is lifted or rotated from its normal position and manipulated for surgical access to the various heart vessels, Obviously, the heart is also stopped when valve repair or replacement is performed and when heart transplant is performed.
The present invention provides apparatus systems and methods which enable any cardiac surgical procedure to be performed while using the patient""s lungs, or at least one lung, for blood oxygenation. This invention enables the surgeon to perform any beating heart, still heart or heart transplant procedure without the use of CPB or other external blood oxygenation equipment or procedure. In its main aspect, this invention enables such non-CPB heart surgery by providing device systems and methods to assure continued pulmonary blood flow through the patient""s lungs or lung and circulatory flow of the oxygenation pulmonary blood through the patient""s body at sufficient levels to sustain the patient during the surgery, regardless of whether the heart is beating with sufficient output, beating with insufficient or partial output or is stopped.
This invention provides for internal and/or external device systems for carrying out the methods of this invention, which device systems are selected and used by the surgeon depending on the cardiac surgical procedure to be performed on the patient. The systems of this invention include three basic systems which can be employed individually or in various combinations to meet the needs of a particular surgical procedure. Each of these systems can be selected and employed in the left side or the right side of the heart, either individually or in combination with another of the systems of this invention. As further illustrated in the description of the invention and exemplified in the drawings herein, the device systems can be positioned for optimal blood flow protection and/or augmentation, i.e., blood intake/inlet positioned in the vein, the atrium or the ventricle and the output/outlet positioned in the ventricle or artery.
The first system of this invention comprises a pump and cannula system wherein the cannula is adapted for insertion through the interior of the heart and/or heart valves to an artery. The right side is through the tricuspid valve and/or pulmonary valve into the pulmonary artery; the left side is through the bicuspid valve and/or aortic valve into the aorta. The pump is adapted as a miniaturized blood pump so it can be positioned close to the heart, either in the open chest cavity or at least in the sterile surgical field, thus providing a minimum priming volume. Alternatively, this system can also be adapted to be inserted into the heart in closed chest procedures through the chest wall as part of a thorascopic procedure, through the femoral vein, the jugular vein or any appropriate access point in the venous system. In these instances the pump is adapted to be positioned as close to the body insertion point as possible in order to keep priming volume to a minimum; for that reason thorascopic or jugular access is preferred when a closed chest procedure is elected. This pump and cannula system is optimally used in both the right and left sides when bypass surgery is initiated, and is employed particularly when the beating heart will need to be lifted, rotated or otherwise manipulated to access lateral or posterior blood vessels, when the heart outflow is cut off by a collapse or kink in the heart chambers or in the veins or arteries, or when the heart is stopped for valve surgery, internal surgery or other reason. This system is also desirable in any heart surgery procedure, even for anterior vessel bypass, when lifting or manipulating of the heart is not anticipated. This applies to both open chest and minimally invasive procedures. This system being put in place in the heart before the cardiac surgery begins, thus assures that the patient will at all times during the surgery have adequate pulmonary blood flow through the lungs and circulatory blood flow throughout the body and will avoid the necessity of being placed on a CPB machine in the event of an unexpected failure of the beating heart to sustain adequate pulmonary or circulatory blood flow during beating heart surgery. This system allows the heart to continue to beat and provide pulmonary and circulatory blood flow to the extent it is capable, until there is a collapse, kink, arrhythmia or arrest, which decreases or stops the blood flow output by the heart. When that occurs, the pump(s) in either or both sides of the heart is/are engaged to supplement the heart produced blood flow or replace the blood flow so that the pulmonary and circulatory blood flows are maintained at a sufficient level to sustain the patient for the duration of the surgery. By having this system in place at the beginning of the beating heart surgery, even for anterior vessel surgery when no need is anticipated, it can merely be engaged or turned on to provide pump assisted blood flow if needed on an unexpected or emergency basis, thus assuring that emergency CPB procedures are avoided. Thus, this system assures that the patient""s lungs are utilized for oxygenation of the blood during the entire surgical procedure, even if an unexpected interruption in blood flow from the beating heart occurs. The system can be also utilized for still heart or stopped heart CABG procedures, where the heart has been stopped by infusing drugs into the patient""s heart, such as cardioplegia or utilizing any other drug that is available that provides the same function. The pump(s) and cannula(s) provide sufficient pulmonary blood circulation to utilize the patient""s lungs for oxygenation and sufficient circulatory blood flow to the body. In this regard, it is noted that one lung is normally sufficient to sustain the patient during surgery. In some procedures the surgeon prefers to collapse one lung to provide additional space inside the chest cavity in which to work. This system accommodates such procedure while sustaining the patient on one lung throughout the surgery and avoiding a CPB machine. Likewise, it is sometimes desired by the surgeon to shrink down the heart by evacuating blood from one or more chambers of the heart, also to provide additional space within the chest cavity in which to work. This system likewise accommodates such procedure, because the pump and cannula system sustain adequate pulmonary and circulatory blood flow throughout the surgical procedure. In this system of this invention the pump in each side is a variable output pump from zero to maximum and is controlled automatically or manually in response to appropriate measurement of blood pressure, blood flow, blood oxygen level, blood CO2 level and/or other desired parameter.
In a second system of this invention, beating heart support is provided to prevent kinking, collapse or undue restriction of blood flow through the beating heart while the heart is manipulated during surgery. This system of devices comprises cannulas and/or stents adapted to be placed in the heart chambers and in the venous and arterial vessels proximate to the heart and in those areas or zones where collapse or kinking during manipulation of the beating heart during surgery is likely to cause restriction in desired pulmonary and/or circulatory blood flow. The devices are placed as desired before or during surgery to allow the beating heart to provide at least a minimum but sufficient pulmonary and circulatory blood flow during surgery. Even when kinking, restriction or collapse of a vein, artery or heart chamber occurs during surgery, the beating heart is still provided a protected passageway equal to the inside diameter of the cannula or stent through which the heart can provide blood flow. In this system no pump is provided and the blood flow is provided solely by the beating heart. By protecting the blood path from restriction or collapse, this system assures the output of the beating heart is available at all times during the surgery to sustain the patient during surgery with sufficient pulmonary and circulatory blood flow. As is apparent, this system is adapted for use exclusively in beating heart procedures. The various types of cannulas/stents with and without check valves and the placement thereof are described in detail below. As mentioned above in connection with the first system of this invention, this second system can be used in conjunction with procedures involving collapsing one lung and/or partially reducing the size of the beating heart to provide additional space in the chest cavity in which the surgeon can work.
The third system of this invention is similar to the above first system in that it comprises a pump and cannula system but is adapted to be placed external of the heart instead of internal in the heart. In this system an intake cannula is adapted for receiving blood from the vein, atrium or ventricle and for passing the blood to the pump, where the blood is passed to an outlet cannula adapted to pass the blood into the artery, all external of the heart. The pump and cannula combinations of this system can be adapted for use in minimally invasive procedures, but are optimally adapted to be miniaturized for placement within the chest cavity or at least within the sterile surgical area to provide a minimum priming volume of the pump and cannula system. This system is optimally used in open chest procedures where the heart will be stopped, such as for value repair or replacement, septum repair or heart transplant. As mentioned above in connection with the first system of this invention, this third system can be used in conjunction with procedures involving collapsing one lung and/or reducing the size of the heart by partially or substantially evacuating one or more chambers of the heart to provide additional space in the chest cavity in which the surgeon can work. As is apparent, this system employs the same type of variable output pump and is controllable in the same manner as in the above first system. This system is adapted to provide sufficient pulmonary and circulatory blood flow in the patient during surgery by either supplementing the beating heart output and/or replacing or substituting for the heart output. This system is adapted to assure sufficient pulmonary and circulatory blood flow and to assure no need for a CPB machine or procedure.
This invention further provides that the above three systems can be selected separately for use in or for the right side and left side of the heart for any particular procedure. For example, the external third system might be used for the right side, while the second or first system is used for the left side, whereby the combination of the two provides sustained and sufficient pulmonary and circulatory blood flow during the cardiac surgical procedure in question. Conversely the external third system might be used for the left side, while the second or first system is used for the right side. One skilled in the art can select the appropriate combinations of the systems following the teaching herein for providing sufficient pulmonary and circulatory blood flow, while avoiding any need for a CPB machine or procedure. Any combination of the three systems could be used in a beating heart, still heart, or when the heart is in any condition there between where the heart is slowed but not completely stopped during the surgical procedure.
The first and second systems and methods of this invention enable beating heart bypass surgery by providing apparatus for protecting the right side from collapse or other restriction, such as ineffective pumping due to heart muscle stress or compression, in order to maintain at least partial pulmonary blood flow through the beating heart, apparatus for augmenting or supplementing the pulmonary and/or circulatory blood flow with a blood pump/cannulation system having a minimum priming volume and, optionally, apparatus for supporting the beating heart in a lifted or manipulated position for bypass surgical access to heart vessels. When desired, the systems and methods of this invention can optionally include apparatus for protecting the left side from collapse to maintain at least partial aortic blood flow through the beating heart and apparatus for supplementing or augmenting the aortic blood flow with a blood pump system having a minimum priming volume. However, in some instances, the aortic circulatory blood flow through the left side of the heart can be sufficiently maintained during beating heart surgery without protecting the left side or supplementing or augmenting the aortic blood flow through the beating heart.
In reference to this invention, xe2x80x9cright sidexe2x80x9d refers to and includes the vena cava veins, the right atrium, the right ventricle, the pulmonary artery and any combination or all thereof, and is referred to as providing the pulmonary blood flow through the lungs. Similarly, xe2x80x9cleft sidexe2x80x9d refers to and includes the pulmonary veins, the left atrium, the left ventricle, the aorta and any combination or all thereof, and is referred to as providing the circulatory blood flow through the body. Also, as used herein vena cava includes superior and inferior vena cava, pulmonary artery and vein includes branches thereof and aorta includes the aortic vessels which are near the heart and are exposed or manipulated during open chest cardiac surgery or are utilized during minimally invasive cardiac surgery.
A major obstacle to performing beating heart bypass surgery on lateral or posterior heart vessels is that when the beating heart is lifted or manipulated to provide surgical access to the lateral or posterior heart vessels, the right side, i.e., the right atrium, or the right ventricle, or both, tends to collapse or diminish in pumping capacity and pulmonary blood flow diminishes to an unacceptably low level and/or the pulmonary artery tends to collapse, kink or become otherwise unduly constricted while the heart is displaced or manipulated. This invention provides apparatus systems and methods for protecting the right side and through the lungs and for maintaining and/or supplementing pulmonary blood flow through the right side and through the lungs while the beating heart is lifted and manipulated for full surgical access to lateral and posterior heart vessels, thus enabling unrestricted beating heart bypass surgery.
In one aspect, this invention provides a system for preventing collapse of the vena cava, right atrium, right ventricle and/or pulmonary artery during beating heart bypass surgery comprising a pump and cannula system wherein the cannula portion is adapted for insertion through the tricuspid valve, through the pulmonary valve and a sufficient length into the pulmonary artery to prevent collapse of the right atrium, right ventricle and/or pulmonary artery and to maintain at best partial blood flow therethrough by the beating heart pumping action while the beating heart is lifted or displaced during surgery. Access for insertion of the cannula portion can be through the vena cava, e.g., from a femoral vein incision, through an incision in the wall of the vena cava or in the wall of the right atrium. If the cannula is not inserted through the tricuspid valve, but only through the pulmonary valve and into the pulmonary artery, access could be through an incision in the wall of the right ventricle or reverse access can be used by entering through an incision in the wall of the pulmonary artery. Separate cannulas can be employed, i.e., one introduced through the right atrium and through the tricuspid valve but ending in the right ventricle, and a second introduced by any desired access and beginning in the right ventricle and extending through the pulmonary valve and a desired length, according to this invention, into the pulmonary artery. The pump portion of the system is adapted for intake of blood upstream of the pulmonary valve or upstream of the tricuspid valve and output of blood into the right ventricle or into the pulmonary artery while the beating heart is displaced during surgery. The pump system is preferably integral with the above cannula or cannulas, particularly in a concentric double wall cannula configuration, or can comprise pump cannulas separate from and in addition to the above cannulas which protect the right side from collapse. The optional cradle system is adapted for supporting the beating heart while the heart is displaced and for providing surgical access to lateral or posterior heart vessels.
In another aspect, this invention further provides an optional embodiment which, in addition to the above system for the right side, a separate pump and cannula system is provided for the left side wherein the cannula portion is adapted for insertion through the bicuspid valve, through the aortic valve and a sufficient length into the aorta to prevent collapse of the pulmonary vein, left atrium, left ventricle and/or aorta and to maintain blood flow therethrough by the beating heart pumping action while the beating heart is lifted or displaced during surgery. As indicated above for the right side, access for the left side cannula or cannulas can be from any desired upstream or downstream incision. One or two cannulas may be employed for preventing collapse of the left side and the pump portion of the system, which may have its separate cannulas, is adapted for intake of blood upstream of the aortic valve or the bicuspid valve and output of blood into the left ventricle or the aorta while the heart is displaced during beating heart surgery.
As is apparent, either the right side system or the left side system or both may be used for a particular patient or procedure. Whether the cannula for pump output extends into the pulmonary artery/aorta or extends only into the respective ventricle will similarly depend on the requirements for a particular patient or procedure. In some instances the beating heart blood flow is impeded due to partial compression, wrinkling or other distortion of the ventricle muscle. Although the muscle is working, it is unable to both fill the ventricle with blood and expel or pump the blood in sufficient quantity. The pump system of this invention can be used by positioning the pump cannula output end in the ventricle to fill or preload the ventricle with blood, so the heart muscle can then pump or expel the blood from the ventricle, even though the muscle is not in its normal shape or position. In this aspect of the invention, beating heart blood flow can be maintained while the heart is displaced during surgery without the necessity of the cannula extending through the pulmonary/aortic valve. The heart may be stopped by short acting drugs that which stop the heart for a short period of time, or by electrical means affecting the electrical conduction of the heart or neurological systems or by use of electrical current to paralyze the nerves responsible for heart beating. While the heart is stopped, the pump(s) will deliver 100% of the necessary blood pulmonary blood flow to and from the lungs and/or 100% of the necessary circulatory blood flow to and from the body without any assistance from the heart. In the event the heart is stopped, and particularly when the heart is opened (such as for valve surgery), it is preferred to provide a seal by balloon sheath cannula, clamp or otherwise to isolate the heart, or at least one side of the heart, at the intake cannula and output cannula so that the pumped blood is directed from the vein to the artery without leakage or backflow into the heart during the surgery. This will enhance the pulmonary and/or circulatory blood flow provided by the pump in the pump and cannula system.
In another aspect, this invention provides a pump and cannula system for use in heart surgery wherein the pump and its cannula system have a priming volume less than about 1,000 ml. Optimally, each individual pump/cannula unit will have a priming volume less than about 100 ml and preferably less than about 50 ml. In one preferred embodiment, the pump and cannula system comprises concentric intake and output conduits, a coaxial cannula, adapted for insertion into a single incision. In another preferred embodiment of this aspect of the invention, the pump and cannula system comprise an intake cannula for insertion in the upstream vessel or heart chamber and an output cannula for insertion downstream into the pulmonary artery or the aorta. In a further preferred embodiment of this aspect the pump and cannula system comprises a miniaturized pump having a sterile drive motor suitable for placement of the pump including the drive motor close to the chest and in the sterile zone, or preferably within the chest cavity itself during the heart surgery. In a further preferred embodiment of this aspect a preferred pump is a reverse flow pump and coaxial cannula combination having a minimum priming volume is used, but a cable driven axial flow pump or other conventional blood pump can be used in this invention.
In another aspect, this invention provides a cannula system for protecting selected portions or all of the right side from collapse during beating heart surgery, an optional cannula system for protecting selected portions or all of the left side from collapse and optional pump and cannula systems for use with the right and/or left side protection cannulas, if needed to supplement or augment the blood flow provided by the beating heart. In some patients all that may be required is the protection cannula or cannulas in the right side to allow the beating heart to maintain sufficient pulmonary and circulatory blood flow during the beating heart bypass surgery and it may not be necessary to use the pump system to provide supplemental pulmonary blood flow and may not be necessary to protect the left side or to provide supplemental circulatory blood flow. For such patients, this invention enables beating heart bypass surgery without artificial pumping of the blood and with minimum invasive apparatus. In some patients, beating heart bypass surgery can be started or attempted with only right side protection cannula(s) in place, then right side supplemental pumping of pulmonary blood flow added during the bypass surgery (or after the surgery) by separately inserting the pump system according to this invention. Likewise, left side protection cannula(s) and/or left side supplemental pumping of arterial blood can be added as needed during (or after) the bypass surgery by insertion of the cannula(s) and/or pump systems according to this invention. Thus, this invention provides optional incremental apparatus that may be selected by the surgeon and used only according to particular patient needs in order to minimize the invasiveness of the bypass surgery procedure.
In another aspect, this invention provides for beating heart surgery a valved cannula having an outside diameter adapted for positioning in the right ventricle through the pulmonary valve and in the pulmonary artery, having blood inlet in the ventricle portion, a blood outlet in the artery portion, a one-way valve or check valve between the inlet and outlet adapted to allow blood flow substantially only in one direction from the inlet toward the outlet and a positioning lead attached to the cannula for holding the cannula in proper position in the heart and the pulmonary artery. This pulmonary valve cannula is adapted to receive blood through the inlet from the right ventricle when the right ventricle contracts and expel the blood through the outlet in the pulmonary artery. The one-way valve is adapted to prevent significant back flow of blood through the cannula back into the right ventricle. The cannula may be adapted and sized to allow blood to flow between the pulmonary valve and the external surface of the cannula when the right ventricle contracts and to allow the pulmonary valve to substantially seal to the external surface of the cannula and prevent significant back flow of blood around the cannula back into the right ventricle, when the right ventricle expands. The portion of the cannula contacting the pulmonary valve can be a different outside diameter than the ventricle portion or the artery portion of the cannula, or both. It may be desirable in some patients to have the outside diameter of the cannula at the pulmonary valve contact portion smaller to allow the maximum beating heart blood flow around the outside of the cannula when the pulmonary valve opens. In other patients it may be desirable to have a larger diameter to maximize the beating heart blood flow through the cannula as opposed to around the cannula. The inlet and outlet can be conventional blood cannula configurations and/or can comprise orifices, slits or other openings at desired locations and intervals along portions of the length of the cannula. The ends or openings can comprise baskets, cages or other guards to prevent suction of heart tissue or blood vessel wall into the cannula. The internal valve in the cannula can be any suitable one-way or check valve, such as a flap valve, slide valve, spring loaded circular valve or ball valve, membrane valve, duck bill valve or other design and can be any material appropriate for a blood flow valve. The positioning lead can be attached to the cannula in any desired way and any desired location and adapted for holding the cannula in position during use. The lead can also be useful in inserting and guiding the cannula through the appropriate vessel incision into proper position. The cannula can be inserted with a guide wire/balloon arrangement from an upstream incision.
In another aspect, this invention provides for beating heart surgery a valved cannula having an outside diameter adapted for positioning in the right atrium through the tricuspid valve and in the right ventricle, having a blood inlet in the atrium portion, a blood outlet in the ventricle portion, a one-way valve or check valve between the inlet and outlet adapted to allow blood flow substantially only in one direction from the inlet toward the outlet and a positioning lead attached to the cannula for holding the cannula in proper position in the heart. This tricuspid valve cannula is adapted to receive blood through the inlet from the right atrium and expel the blood through the outlet in the right ventricle when the right ventricle expands. The one-way valve is adapted to prevent significant back flow of blood through the cannula back into the right atrium when the right ventricle contracts. The cannula is preferably adapted and sized to allow blood to flow between the tricuspid valve and the external surface of the cannula when the right ventricle expands and to allow the tricuspid valve to substantially seal to the external surface of the cannula and prevent significant back flow of blood around the cannula back into the right ventricle when the right ventricle contracts. The portion of the cannula contacting the tricuspid valve can be a different outside diameter than the atrium portion or the ventricle portion of the cannula, or both. It may be desirable in some patients to have the outside diameter of the cannula at the tricuspid valve contact portion smaller to allow the maximum beating heart blood flow around the outside of the cannula when the tricuspid valve opens. In other patients it may be desirable to have a larger diameter to maximize the beating heart blood flow through the cannula as opposed to around the cannula. The inlet and outlet can be conventional blood cannula configuration and/or can comprise orifices, slits or other openings at desired locations and intervals along portions of the length of the cannula basket or cage to prevent heart tissue suction. The ends or openings can comprise baskets, cages or other guards to prevent suction of heart tissue or blood vessel wall into the cannula. The internal valve in the cannula can be any suitable one-way or check valve, such as a flap valve, slide valve, spring loaded circular valve or ball valve, membrane valve, duck bill valve or other design and can be any material appropriate to a blood flow valve. The positioning lead can be attached to the cannula in any desired way and any desired location and adapted for holding the cannula in position during use. The lead can also be useful in inserting and guiding the cannula through the appropriate vessel incision into proper position. The cannula can be inserted with a guide wire/balloon arrangement from an upstream incision.
In another aspect of this invention, the above pulmonary valve cannula and the above tricuspid valve cannula may be combined or formed as a single cannula adapted to the position through both the tricuspid and pulmonary valves with the respective check valves, inlets and outlets properly positioned according to the functions set forth above for each. The advantages of this single cannula configuration include single incision, single guide wire and single positioning lead.
In another aspect, this invention provides apparatus for supporting and preventing collapse of the kink zone in the pulmonary artery. In addition to apparatus for supporting and preventing collapse of the right atrium and right ventricle, this invention provides a separately adapted stent to prevent collapse or kinking of the pulmonary artery to maintain blood flow through the pulmonary artery and/or through the stent during beating heart bypass surgery. When the beating heart is lifted and manipulated for surgical access to the posterior or lateral blood vessels, the pulmonary artery tends to fold or kink and restrict or stop the beating heart blood flow. A clamp or stabilizer can be applied to the external surface of the heart to take in the slack from the heart muscle and allow the muscle to function and to generate the contraction to eject blood even if the heart muscle is wrinkled.
As used herein the pulmonary artery xe2x80x9ckink zonexe2x80x9d is the portion of the pulmonary artery between the heart and the lungs where the artery tends to fold, kink or restrict when the beating heart is lifted or manipulated for surgical access to the lateral or posterior heart vessels. This kink zone is in the portion of the pulmonary artery within about 15 cm from the heart and usually within about 10 cm.
In this aspect of the invention, the pulmonary artery stent is adapted to have diameter and length appropriate to extend the length of the kink zone and an appropriate distance on either side of the kink zone to assure full protection of the pulmonary artery during a beating heart surgical procedure. The pulmonary artery stent also comprises a handle for inserting and withdrawing the stent through an appropriate incision. Typically the stent will further comprise a guide wire/balloon for placement of the stent in the proper position in the pulmonary artery. In some patients the pulmonary artery stent may be all that is required to protect the left side during a particular beating heart surgical procedure. In other instances the beating heart surgery may require only the pulmonary artery stent and the above tricuspid valve,cannula. In other instances, the use of a pump and cannula system described above may be needed to supplement or augment the right side flow of blood produced by the beating heart during bypass surgery.
This invention further provides the above stent adapted for positioning in other portions of the right side to prevent collapse or restriction in a similar xe2x80x9ckink zonexe2x80x9d in the vena cava veins, right atrium or right ventricle and to maintain pulmonary blood flow through the right side while the heart is displaced and manipulated during beating heart bypass surgery. As is apparent, the above stent may also be adapted for positioning in the aorta, pulmonary veins, left atrium and/or left ventricle to maintain aortic beating heart blood flow during beating heart bypass surgery.
As is apparent, this invention enables the use of various combinations of the above aspects of this invention to meet the requirements of a particular patient for the successful performance of beating heart or still heart surgery while assuring that the patient""s lungs (or lung) provides the oxygenated blood to sustain the patient through the surgery and that a CPB machine and procedure is avoided. Selective use of the above stents, cannulas and/or pump and cannula systems in their various configurations results in minimum invasiveness and minimum contact of the blood with apparatus in or outside the body during beating heart bypass surgery. Thus, this invention enables all beating and still heart surgical procedures without the use of a CPB machine by providing methods and apparatus systems ranging from one or more stents placed to prevent restriction of blood flow produced by the beating heart to pump and cannula systems placed through or around the entire right side and through or around the entire left side to both protect the beating heart blood flow and to augment, supplement or, when necessary, temporarily replace the beating heart blood flow during the surgery.
In preferred embodiments of this invention, the cradle for supporting the beating heart during beating heart bypass surgery can be a flexible film or mesh, or it can be a rigid or semi-rigid member with appropriate openings. The cradle not only provides support for the beating heart in the desired and necessary position for surgical access to heart vessels, it also provides visual access to the appropriate heart vessels on which the bypass surgery is performed.
In another aspect, this invention provides a method for sustaining sufficient blood flow in the patient during heart surgery which comprises:
inserting the cannula portion of a pump and cannula system through the interior of one side of the heart to extend the cannula into the artery or aorta; and
adjusting the pump output during the surgery to provide sufficient blood flow in the patient during the surgery. The blood flow referred to in this method can be the pulmonary blood flow through the lungs (or lung) or the circulatory blood flow from the aorta through the body. The cannula and pump system may preferably be placed in and used in both sides of the heart.
In another aspect, this invention provides a method for performing beating heart surgery which comprises:
inserting in the right side of the heart a cannula or stent adapted to protect the blood flow path through the heart when the stented portion of the heart is collapsed or kinked; and
performing beating heart bypass surgery while the cannula(s) or stent(s) is in place in the heart. Such cannula or stent may be placed in any portion of or all of the right side of the heart before the surgery is performed. Likewise the cannula(s) or stent(s) may be placed also, or instead, in the left side of the heart before the surgery is performed.
In another aspect, this invention provides a method for performing heart surgery which comprises:
inserting the cannula portion of a pump and cannula system through the tricuspid valve, through the pulmonary valve and a sufficient length into the pulmonary artery to prevent collapse of the right atrium, right ventricle or pulmonary artery when the heart is lifted or displaced during surgery;
pumping blood from upstream of the pulmonary valve into the pulmonary artery whereby the combined flow of blood through the pulmonary artery produced by the beating heart and the pump is sufficient to sustain the patient during surgery; and
optionally supporting the beating heart in a cradle to provide surgical access to the lateral or posterior heart vessels.
In another embodiment, this invention provides a system for preventing collapse of the right atrium, right ventricle or pulmonary artery and maintaining blood flow across the pulmonary valve and into the pulmonary artery during heart surgery comprising:
a cannula adapted for insertion through the tricuspid valve, through the pulmonary valve and a sufficient length into the pulmonary artery to prevent collapse of the right atrium, right ventricle or pulmonary artery while the beating heart is lifted or displaced during surgery;
a pump and cannula system adapted for removing blood from the vena cava or the right atrium and transporting the blood through a cannula and into the pulmonary artery; and
optionally a cradle for supporting the beating heart while the heart is displaced during surgery and for providing surgical access to lateral or posterior heart vessels. The pump and cannula system can be part of or utilize the cannula adapted for insertion, or can be a separate pump and cannula external of the heart.
In another aspect, this invention provides a method for performing heart surgery which comprises:
connecting a pump intake tube through an incision in the wall of the vena cava or the right atrium to remove blood from the vena cava or the right atrium;
connecting the pump outflow tube into the pulmonary artery through an incision in the wall of the pulmonary artery;
pumping blood from the right atrium through the pump into the pulmonary artery; and
optionally supporting the beating heart in a cradle during surgery for surgical access to the heart vessels. When this method is used for still heart surgical procedures, the method further optionally comprises isolating the heart to prevent venus blood flow into the heart and to prevent backflow of arterial blood into the heart during at least a portion of the surgical procedure.
As is apparent, this invention provides and enables various embodiments of methods for beating heart bypass surgery utilizing the various selected combinations of the above described stents, cannulas and pump and cannula systems as appropriate for a particular patient or procedure following the disclosures of this invention and enables heart surgery without the use of CPB machines.